mm: fix invalid use of pfn_valid_within in test_pages_in_a_zone

Offlining memory by 'echo 0 > /sys/devices/system/memory/memory#/online'
or reading valid_zones 'cat
/sys/devices/system/memory/memory#/valid_zones' causes BUG: unable to
handle kernel paging request due to invalid use of pfn_valid_within.  This
is due to a bug in test_pages_in_a_zone.

In order to use pfn_valid_within within a MAX_ORDER_NR_PAGES block of
pages, a valid pfn within the block must first be found.  There only needs
to be one valid pfn found in test_pages_in_a_zone in the first place.  So
the fix is to replace pfn_valid_within with pfn_valid such that the first
valid pfn within the pageblock is found (if it exists).  This works
independently of CONFIG_HOLES_IN_ZONE.

Signed-off-by: James Custer <jcuster@sgi.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Russ Anderson <rja@sgi.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 457bde530cbedcf0dea2f35e219466de0acf204d..c6a8d95c5dc7d36cfa3263e05b0bc2368667b849 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1332,7 +1332,7 @@ int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
 }
 
 /*
- * Confirm all pages in a range [start, end) is belongs to the same zone.
+ * Confirm all pages in a range [start, end) belong to the same zone.
  */
 int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
 {
@@ -1343,10 +1343,11 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
        for (pfn = start_pfn;
             pfn < end_pfn;
             pfn += MAX_ORDER_NR_PAGES) {
-               i = 0;
-               /* This is just a CONFIG_HOLES_IN_ZONE check.*/
-               while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
-                       i++;
+               /* Find the first valid pfn in this pageblock */
+               for (i = 0; i < MAX_ORDER_NR_PAGES; i++) {
+                       if (pfn_valid(pfn + i))
+                               break;
+               }
                if (i == MAX_ORDER_NR_PAGES)
                        continue;
                page = pfn_to_page(pfn + i);